Johnson, who will sign when his Rams contract expires in July, started his career at Meadow Lane and is delighted to be back.
He added: "It may or may not be my last year as a professional footballer but I'm definitely not looking to pick up some easy wages.
"Everyone knows that it was always in my mind to come back and finish my career at Meadow Lane but I'm determined to do it in the right way.
"I like to think that I played my part in preventing us from slipping out of the League and now I want to be involved in moving us forward.
"Ideally, of course, I want to see us mount a promotion challenge but we have to be realistic.
"There's an awful lot that needs to change before Notts County get back to where we were and it's essential that people recognise that. Things won't change overnight."